U.S. patent application number 12/188542 was filed with the patent office on 2009-06-11 for method and apparatus of downstream service flows classification for headend cable modem.
Invention is credited to Dong Joon CHOI, O Hyung KWON, Ho-Sook LEE, Soo In LEE, Hye Ju OH.
Application Number | 20090147788 12/188542 |
Document ID | / |
Family ID | 40721614 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090147788 |
Kind Code |
A1 |
LEE; Ho-Sook ; et
al. |
June 11, 2009 |
METHOD AND APPARATUS OF DOWNSTREAM SERVICE FLOWS CLASSIFICATION FOR
HEADEND CABLE MODEM
Abstract
A method and apparatus of classifying downstream service flows
for a cable modem is provided. A method of classifying downstream
service flows, the method including: classifying a service flow
based on a Quality of Service (QoS) using a destination address of
an inputted packet; composing an internal header including
corresponding service flow information based on the classifying of
the service flow; and adding the internal header to the inputted
packet.
Inventors: |
LEE; Ho-Sook; (Daejeon,
KR) ; OH; Hye Ju; (Daejeon, KR) ; CHOI; Dong
Joon; (Daejeon, KR) ; KWON; O Hyung; (Daejeon,
KR) ; LEE; Soo In; (Daejeon, KR) |
Correspondence
Address: |
LADAS & PARRY LLP
224 SOUTH MICHIGAN AVENUE, SUITE 1600
CHICAGO
IL
60604
US
|
Family ID: |
40721614 |
Appl. No.: |
12/188542 |
Filed: |
August 8, 2008 |
Current U.S.
Class: |
370/392 |
Current CPC
Class: |
H04L 47/2433 20130101;
H04L 47/10 20130101; H04L 47/31 20130101; H04L 47/2408 20130101;
H04L 47/2441 20130101 |
Class at
Publication: |
370/392 |
International
Class: |
H04L 12/56 20060101
H04L012/56 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2007 |
KR |
10-2007-0125474 |
Claims
1. A method of classifying downstream service flows, the method
comprising: classifying a service flow based on a Quality of
Service (QoS) using a destination address of an inputted packet;
composing an internal header including corresponding service flow
information based on the classifying of the service flow; and
adding the internal header to the inputted packet.
2. The method of claim 1, wherein the classifying extracts the
destination address of the inputted packet, and acquires service
flow classification information based on the destination address
and QoS information included in the inputted packet.
3. The method of claim 2, wherein the service flow classification
information is provided from a service flow classification table to
search for the service flow information using a search word
including an address of a cable modem (CM), the address
corresponding to the destination address, and the QoS
information.
4. The method of claim 2, wherein the corresponding service flow
information is provided from a service flow information table to
search for the service flow information using a reference address
corresponding to the service flow classification information.
5. The method of claim 4, wherein the service flow information
table includes at least one of priority information of the service
flow corresponding to the reference address, a Downstream Service
Identification (DSID), and Downstream Channel (DC) list
information.
6. A method of classifying downstream service flows, the method
comprising: extracting a destination address of an input packet;
determining whether an Ethernet Media Access Control (MAC) address
of a CM to which the input packet is transmitted exists, using the
destination address; composing a search character string based on
QoS information included in the Ethernet MAC address of the CM and
the input packet when the Ethernet MAC address of the CM
corresponding to the destination address exists; searching for a
reference address corresponding to the search character string and
searching for service flow information based on the retrieved
reference address when the reference address is retrieved; and
composing an internal header including the retrieved service flow
information and adding the internal header to the input packet.
7. The method of claim 6, wherein, when the Ethernet MAC address of
the CM corresponding to the destination address does not exist, the
input packet is processed as data to be broadcasted.
8. The method of claim 6, wherein, when the reference address
corresponding to the search character string is not retrieved,
basic service flow information, the basic service flow information
being about the CM to which the input packet is transmitted, is
extracted, and the extracted basic service flow information is
included in the internal header, and the internal header is added
to the input packet.
9. The method of claim 6, wherein, when at least two reference
addresses corresponding to the search character string are
retrieved, the service flow information is retrieved based on the
reference address located in a top address.
10. An apparatus for classifying downstream service flows, the
apparatus comprising: a downstream service flow classifier to
receive service flow information about an input packet, and to add
an internal header; a service flow classification table to receive
a search character string from the downstream service flow
classifier, to search for reference address information for
searching for the service flow information, and to provide the
downstream service flow classifier with the retrieved reference
address information; and a service flow information table to
provide the downstream service flow classifier with the service
flow information corresponding to the retrieved reference address
information.
11. The apparatus of claim 10, further comprising: an address table
to provide the downstream service flow classifier with address
information of a CM corresponding to a destination address of the
input packet.
12. The apparatus of claim 11, wherein the search scheme is
composed by the address information of the CM and QoS information
included in the input packet.
13. The apparatus of claim 10, wherein the service flow information
table includes at least one of priority information of a service
flow corresponding to the reference address information, a DSID,
and DC list information.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Korean Patent
Application No. 10-2007-0125474, filed on Dec. 5, 2007, in the
Korean Intellectual Property Office, the entire disclosure of which
is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to downstream service flow
processing in a network, for example, a Hybrid Fiber Coax (HFC)
network, and more particularly, to a method and apparatus of
classifying a cable modem (CM) to which a packet is transmitted,
with respect to downstream packets transmitted from a network
service interface to a Cable Modem Termination System (CMTS)
located in a headend, and classifying a service flow to transmit
the packet based on a classification rule of a corresponding
CM.
[0004] This work was supported by the IT R&D program of
MIC/IITA [2006-S-019-02, The Development of Digital Cable
Transmission and Receive System for 1 Gbps Downstream].
[0005] 2. Description of Related Art
[0006] A Hybrid Fiber Coax (HFC) network is a network including an
optical fiber and a coaxial cable, and is a broadband transmission
network to transmit a data signal (the Internet, a cable television
(TV), crime prevention, disaster prevention, remote inspection of a
meter, and automatic control) using the optical fiber to a
broadcasting station and an Optical Network Unit (ONU), and using
the coaxial cable from the ONU to members.
[0007] A downstream data packet inputted using a network interface
in a cable network following Data Over Cable Service Interface
Specifications (DOCSIS) must be transmitted to a receivable channel
of a corresponding cable modem (CM) in order to transmit the
downstream data packet to a specific CM.
[0008] A channel transmittable to the corresponding CM may be one,
or may be a plurality of channels when supporting channel bonding.
Downstream packets are classified into service flows in accordance
with each Quality of Service (QoS) and are scheduled to the channel
transmittable to the CM.
[0009] Accordingly, a Cable Modem Termination System (CMTS) must
allocate and classify the service flows based on the QoS requested
from the CM.
[0010] A single CM may admit a plurality of service flows, and a
single channel must transmit the plurality of service flows. When
the CM receives downstream data by a plurality of channels using
the channel bonding, a single service flow may be distributed into
the plurality of channels using a bonded channel group and be
transmitted.
[0011] Accordingly, all downstream packets in the HFC network
following DOCSIS must be classified into service flows and be
scheduled to a channel by which the corresponding service flow from
among various downstream channels of the CMTS is transmittable.
SUMMARY OF THE INVENTION
[0012] An aspect of the present invention provides a method and
apparatus of classifying downstream service flows which can
classify a Media Access Control (MAC) address of a cable modem (CM)
to which a packet is transmitted, using a destination MAC address
of downstream data packets in an Institute of Electrical and
Electronics Engineers (IEEE) 802.3 MAC/DEC-Intel-Xerox (DIX)
configuration, the downstream data packets transmitted from a
network interface to a Cable Modem Termination System (CMTS) in a
Data Over Cable Service Interface Specifications (DOCSIS)-based
cable network.
[0013] Another aspect of the present invention also provides a
method and apparatus of classifying downstream service flows which
can compose a search pattern to search for a service flow using a
CM MAC address and an upper data portion of an inputted packet.
[0014] Another aspect of the present invention also provides a
method of classifying a service flow to be transmitted, the service
flow corresponding to a Quality of Service (QoS) of a downstream
packet from a service flow classification table, and an information
table for service flow classification.
[0015] Another aspect of the present invention also provides a
method of transmitting service flow information to a downstream
packet scheduling block, an information table structure and
relation to embody the above-described schemes, and a structure of
related materials.
[0016] According to an aspect of the present invention, there is
provided a method of classifying downstream service flows, the
method including: classifying a service flow based on a Quality of
Service (QoS) using a destination address of an inputted packet;
composing an internal header including corresponding service flow
information based on the classifying of the service flow; and
adding the internal header to the inputted packet.
[0017] According to another aspect of the present invention, there
is provided a method of classifying downstream service flows, the
method including: extracting a destination address of an input
packet; determining whether an Ethernet MAC address of a CM to
which the input packet is transmitted exists, using the destination
address; composing a search character string based on QoS
information included in the Ethernet MAC address of the CM and the
input packet when the Ethernet MAC address of the CM corresponding
to the destination address exists; searching for a reference
address corresponding to the search character string and searching
for service flow information based on the retrieved reference
address when the reference address is retrieved; and composing an
internal header including the retrieved service flow information
and adding the internal header to the input packet.
[0018] According to still another aspect of the present invention,
there is provided an apparatus for classifying downstream service
flows, the apparatus including: a downstream service flow
classifier to receive service flow information about an input
packet, and to add an internal header; a service flow
classification table to receive a search character string from the
downstream service flow classifier, to search for reference address
information for searching for the service flow information, and to
provide the downstream service flow classifier with the retrieved
reference address information; and a service flow information table
to provide the downstream service flow classifier with the service
flow information corresponding to the retrieved reference address
information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other aspects of the present invention will
become apparent and more readily appreciated from the following
detailed description of certain exemplary embodiments of the
invention, taken in conjunction with the accompanying drawings of
which:
[0020] FIG. 1 illustrates a downstream service flow transmission
concept according to an exemplary embodiment of the present
invention;
[0021] FIG. 2 illustrates an apparatus for classifying downstream
service flows according to an exemplary embodiment of the present
invention;
[0022] FIG. 3 illustrates a configuration of an input packet
according to an exemplary embodiment of the present invention;
[0023] FIG. 4 illustrates a configuration example of an information
table for classifying downstream service flows according to an
exemplary embodiment of the present invention;
[0024] FIG. 5 is a flowchart illustrating a packet classification
process of a downstream service flow classifier according to an
exemplary embodiment of the present invention; and
[0025] FIG. 6 illustrates an output packet format of a downstream
service flow classifier according to an exemplary embodiment of the
present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0026] Reference will now be made in detail to exemplary
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The exemplary
embodiments are described below in order to explain the present
invention by referring to the figures.
[0027] When detailed descriptions related to a well-known related
function or configuration are determined to make the spirits of the
present invention ambiguous, the detailed descriptions will be
omitted herein. Also, terms used throughout the present
specification are used to appropriately describe exemplary
embodiments of the present invention, and thus may be different
depending upon a user and an operator's intention, or practices of
application fields of the present invention. Therefore, the terms
must be defined based on descriptions made through the present
invention.
[0028] FIG. 1 illustrates a downstream service flow transmission
concept according to an exemplary embodiment of the present
invention.
[0029] Referring to FIG. 1, a Cable Modem Termination System Media
Access Control (CMTS MAC) layer of a headend includes a service
flow classification unit and a scheduling and distribution
unit.
[0030] The service flow classification unit includes a downstream
service flow classifier 101.
[0031] The downstream service flow classifier 101 classifies
downstream data packets 102 in an Institute of Electrical and
Electronics Engineers (IEEE) 802.3 MAC/DEC-Intel-Xerox (DIX)
configuration by a service flow unit, the downstream data packets
102 being transmitted from a Data Over Cable Service Interface
Specifications (DOCSIS)-based Hybrid Fiber Coax (HFC) network to a
Cable Modem Termination System (CMTS).
[0032] The downstream service flow classifier 101 classifies a
service flow 103 by which a packet is served, based on a Quality of
Service (QoS) of each packet
[0033] The scheduling and distribution unit includes a realignment
unit 104 to realign downstream packets 103 classified by a
downstream service for supporting a channel bonding function and a
distributor 105 to perform scheduling and distribution based on a
transmission policy classified by the service flow. Here, service
flow information is classified in the downstream packets 103.
[0034] The downstream packets are distributed (106) to a downstream
channel to which the downstream packets are transmitted, based on
the scheduling performed by the distributor 105, and are
transmitted to a cable modem (CM).
[0035] A configuration of an outputted packet is a frame in which a
DOCSIS MAC header for transmission in the HFC network is added to
an upper portion of a packet.
[0036] A method of classifying downstream service flows according
to an exemplary embodiment of the present invention classifies a
service flow based on a QoS using a destination address of an
inputted packet, composes an internal header including
corresponding service flow information based on the classifying of
the service flow, and adds the internal header to the inputted
packet.
[0037] FIG. 2 illustrates an apparatus 200 for classifying
downstream service flows according to an exemplary embodiment of
the present invention.
[0038] Referring to FIG. 2, the apparatus 200 for classifying the
downstream service flows includes a downstream service flow
classifier 201, a CM MAC address search table 202, a service flow
classification table 203, and a service flow information table
204.
[0039] The downstream service flow classifier 201 receives service
flow information about an input packet, and adds an internal
header.
[0040] According to an exemplary embodiment of the present
invention, the downstream service flow classifier 201 classifies a
service flow with respect to an input packet in an IEEE 802.3
MAC/DIX configuration transmitted from a network interface based on
a QoS, and transmits, to a function block for downstream
transmission scheduling, a frame in which the service flow
information is added to the internal header.
[0041] According to an exemplary embodiment of the present
invention, as illustrated in FIG. 3, a packet format of the input
packet includes a destination address 301.
[0042] The packet format of the frame in which the internal header
is added is illustrated in FIG. 6.
[0043] The downstream service flow classifier 201 identifies a CM
including a destination node required to transmit a packet from the
CM MAC address search table 202 using a destination MAC address of
an inputted packet, as an additional service node.
[0044] The CM MAC address search table 202 includes a CM MAC
address and an Ethernet MAC address with respect to service nodes
included in the CM. Accordingly, the CM MAC address search table
202 is composed to search for the Ethernet MAC address of the CM to
which the packet is transmitted, from a destination address to
which the input packet is transmitted.
[0045] The downstream service flow classifier 201 identifies a
header portion of the packet including a QoS classification
characteristic included in the packet with respect to a downstream
packet of classifying the CM to which the packet is transmitted,
and classifies the service flow from the service flow
classification table 203.
[0046] The service flow classification table 203 is composed to
return a reference address of the service flow information table
204 including the service flow information using input packet data
and the CM MAC address as a search word.
[0047] The downstream service flow classifier 201 adds the related
service flow information with respect to the input packet in which
the service flow is classified, as an internal header
configuration, and finally outputs the service flow information to
a downstream scheduling block.
[0048] According to an exemplary embodiment of the present
invention, the CM MAC address search table 202 may include an
element of a Content Addressable Memory (CAM) function to search
for contents once, the contents being intended to be retrieved, or
a Ternary Content Addressable Memory (TCAM) function to be used for
a network search engine.
[0049] According to an exemplary embodiment of the present
invention, the service flow classification table 203 is embodied
using a memory of a TCAM scheme to search for contents when a data
character string of a specific location is the same.
[0050] The service flow information table 204 may be embodied as a
Random Access Memory (RAM)-based memory to perform search using an
address of related information.
[0051] FIG. 4 illustrates a configuration example of an information
table for classifying downstream service flows according to an
exemplary embodiment of the present invention.
[0052] Referring to FIG. 4, a CM MAC address search table 401
provides the downstream service flow classifier 201 with address
information of a CM corresponding to a destination address of the
input packet.
[0053] The CM MAC address search table 401 may include a table to
output a 6-byte CM MAC address 403 to which a packet is
transmitted, with respect to a destination MAC address 402 of a
6-byte input packet.
[0054] CM MAC address registration with respect to service nodes
included in a CM may be embodied using presetting by an operator's
request, an address training function by a layer-2 (L2) protocol,
and the like.
[0055] The downstream service flow classifier 201 includes a search
character string 404 to extract and add, from an upper bit, all
data areas including QoS information for classification from among
the retrieved CM MAC address and input packet data, and to search
for a service flow classification table 405.
[0056] The service flow classification table 405 of FIG. 4 is an
information table embodied as a TCAM scheme used for a network
search engine.
[0057] The service flow classification table 405 may include a
memory to output an address of an entry located in a top address
matched with the inputted search character string as a search
result.
[0058] The service flow classification table 405 may include a data
array 406 including a search pattern and a mask array 407 of the
same length as a data array to indicate locations of data bits
desired to be matched from among data arrays as `1`.
[0059] The mask array 407 is composed to be the same length as the
search character string 404.
[0060] A search principle using the search character string 404
outputs an address with respect to data in which all character
strings of a location being set as `1` in the mask array from among
data arrays are same as the search character string when the search
character string is inputted.
[0061] When at least one data array in accordance with the
above-described condition exists, an address of the data array
located in an upper address is outputted. When at least two
addresses corresponding to the search character string 404 are
retrieved, an address located in the top address is outputted.
[0062] When a corresponding data array does not exist, the service
flow classification table 405 outputs a search failure signal.
[0063] Address information of the data array outputted as a search
result from the service flow classification table 405 may be used
for a reference (a reference address) of a downstream service flow
information table 409.
[0064] Since each entry of the service flow classification table
405 is related with each entry of the downstream service flow
information table 409 one-to-one, the address information of the
data array outputted from the service flow classification table 405
may be used for the reference address.
[0065] The downstream service flow classifier 201 calculates a
location of the data array acquired by the search result of the
service flow classification table 405 using a predetermined rule,
and uses the calculated location of the data array for the address
of the memory in which the downstream service flow information
table 409 is located.
[0066] The downstream service flow information table 409 includes
at least one of information about whether a channel bonding service
is supported for each service flow, information about a DOCSIS
header type to be composed (Pkt Type), a Downstream Service
Identification (DSID), a priority to be applied to transmission
scheduling, and Downstream Channel (DC) list information to be
provided with a downstream transmission service.
[0067] FIG. 5 is a flowchart illustrating a packet classification
process of a downstream service flow classifier according to an
exemplary embodiment of the present invention.
[0068] Referring to FIG. 5, the packet classification process of
the downstream service flow classifier includes extracting a
destination address of an input packet in operation S501,
determining whether an Ethernet MAC address of a CM to which the
input packet is transmitted exists, using the destination address
in operations S502 and S503, composing a search character string
based on QoS information included in the Ethernet MAC address of
the CM and the input packet in operation S504 when the Ethernet MAC
address of the CM corresponding to the destination address exists,
searching for a reference address corresponding to the search
character string and searching for service flow information based
on the retrieved reference address in operations S505, S506, and
S507 when the reference address is retrieved, and composing an
internal header including the retrieved service flow information,
adding the internal header to the input packet, and transmitting a
downstream packet to a downstream channel scheduling unit in
operations S508 and S509.
[0069] In operation S501, when a packet in an IEEE 802.3 MAC/DIX
configuration reaches from a network interface to a MAC processing
unit of a headend CM, the downstream service flow classifier 201
extracts a destination address field from among Ethernet MAC
address fields of the reached packet.
[0070] In operations S502 and S503, the downstream service flow
classifier 201 searches for a CM MAC address search table, and
determines whether a corresponding address exists.
[0071] In operation S504, when the corresponding address exists,
the downstream service flow classifier 201 acquires a MAC address
of the CM to which the input packet is transmitted, extracts the
acquired MAC address and a data field to a set location from among
tipper data fields of the input packet, and composes the search
character string.
[0072] In operations S505 and S506, the downstream service flow
classifier 201 searches for the service flow classification table
405 using the search character string.
[0073] In operation S507, when a corresponding data array exists,
the downstream service flow classifier 201 extracts service
flow-related information from the downstream service flow
information table 409 using a retrieved index.
[0074] In operation S508, after the downstream service flow
classifier 201 composes internal header information based on the
service flow information, the downstream service flow classifier
201 adds the internal header to an upper portion of the input
packet and generates information of an output packet.
[0075] In operation S509, the downstream service flow classifier
201 transmits, to the downstream channel scheduling unit, the
downstream packet in which the internal header is added.
[0076] In operation S510, when a corresponding service flow cannot
be found in operation S506, the downstream service flow classifier
201 classifies the service flow as a basic service flow of the
corresponding CM, and repeatedly performs operations from operation
S507 using the basic service flow as an index of a predetermined
service flow information table of a basic service flow information
location.
[0077] Since failing in finding information of the CM to which the
inputted packet is transmitted in operation S503 denotes a packet
transmitted to an unknown address, the service flow is classified
as a broadcast service flow based on a transmission rule of IEEE
802.1 in operation S511.
[0078] Accordingly, in operation S511, the downstream service flow
classifier 201 repeatedly performs operations from operation S507
using the index of the predetermined service flow information table
for the broadcast service flow.
[0079] In operations S501 through S511, even when a plurality of
classifiers exists in the CM, the service flow classification
process is similarly performed. The service flow classification
process is not performed based on a priority of a classifier until
corresponding information is found.
[0080] According to an exemplary embodiment of the present
invention disposes a classifier having a high priority in an upper
location when classification information is inputted in the service
flow classification table. Therefore, when at least one
corresponding data array is generated, a repeated classification
process is enabled not to be performed by outputting the data array
located in the upper portion even when the plurality of classifiers
exists.
[0081] As described above, the downstream service flow classifier
201 according to an exemplary embodiment of the present invention
composes service flow classification information including data
acquired from the service flow information table, and composes the
internal header.
[0082] As illustrated in FIG. 6, the packet format including the
internal header may be added to the upper portion of the input
packet.
[0083] Referring to FIG. 6, information included in the internal
header may include DOCSIS header type information (Pkt Type) 601, a
priority 602 applied to transmission scheduling, a DSID 603, and DC
list information 604 to be provided with a downstream transmission
service.
[0084] The information included in the internal header is used for
determining a downstream channel to which a packet is transmitted,
composing a complete DOCSIS MAC frame, and transmitting the DOCSIS
MAC frame to a CM.
[0085] An exemplary embodiment of the present invention provides a
method of classifying a CM to which downstream data packets
inputted in an IEEE 802.3 MAC/DIX or IEEE 802.1P/Q configuration
are transmitted from a network interface, a method of classifying
an inputted packet into a specific service flow based on a
classification rule classified by a service flow of a corresponding
CM, a method of transmitting classified service flow information to
a downstream packet scheduling block of a CMTS MAC layer, and a
portion with respect to a data structure to embody the methods. A
portion with respect to a control function related to
generation/deletion of the service flow and a scheme of scheduling
to a downstream channel is excluded from a category of the present
invention.
[0086] The method of classifying the downstream service flows
according to the above-described exemplary embodiments may be
recorded in computer-readable media including program instructions
to implement various operations embodied by a computer. The media
may also include, alone or in combination with the program
instructions, data files, data structures, and the like. The media
and program instructions may be those specially designed and
constructed for the purposes of the present invention, or they may
be of the kind well-known and available to those having skill in
the computer software arts. Examples of computer-readable media
include magnetic media such as hard disks, floppy disks, and
magnetic tape; optical media such as CD ROM disks and DVD;
magneto-optical media such as optical disks; and hardware devices
that are specially configured to store and perform program
instructions, such as read-only memory (ROM), random access memory
(RAM), flash memory, and the like. Examples of program instructions
include both machine code, such as produced by a compiler, and
files containing higher level code that may be executed by the
computer using an interpreter. The described hardware devices may
be configured to act as one or more software modules in order to
perform the operations of the above-described embodiments of the
present invention.
[0087] According to the present invention, it is possible to
simplify a configuration of a data information table used for
packet classification when classifying a packet inputted from a
network interface by a service flow to be transmitted, and minimize
a packet classification time with respect to inputted packets.
[0088] Also, according to the present invention, it is possible to
classify a service flow based on a priority using a single search
without a repeated classification process even when at least one
classifier is set for each CM.
[0089] Also, according to the present invention, it is possible to
enhance easiness of hardware embodiment, thereby being effectively
used for a downstream frame processing system composing a CMTS MAC
layer.
[0090] Although a few exemplary embodiments of the present
invention have been shown and described, the present invention is
not limited to the described exemplary embodiments. Instead, it
would be appreciated by those skilled in the art that changes may
be made to these exemplary embodiments without departing from the
principles and spirit of the invention, the scope of which is
defined by the claims and their equivalents.
* * * * *